/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: WalkingIterator.java,v 1.2.4.2 2005/09/14 19:45:19 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.utils.PrefixResolver;
import com.sun.org.apache.xpath.internal.Expression;
import com.sun.org.apache.xpath.internal.ExpressionOwner;
import com.sun.org.apache.xpath.internal.VariableStack;
import com.sun.org.apache.xpath.internal.XPathVisitor;
import com.sun.org.apache.xpath.internal.compiler.Compiler;
import com.sun.org.apache.xpath.internal.compiler.OpMap;

/**
 * Location path iterator that uses Walkers.
 */

public class WalkingIterator extends LocPathIterator implements ExpressionOwner {

  static final long serialVersionUID = 9110225941815665906L;

  /**
   * Create a WalkingIterator iterator, including creation
   * of step walkers from the opcode list, and call back
   * into the Compiler to create predicate expressions.
   *
   * @param compiler The Compiler which is creating this expression.
   * @param opPos The position of this iterator in the opcode list from the compiler.
   * @param shouldLoadWalkers True if walkers should be loaded, or false if this is a derived
   * iterator and it doesn't wish to load child walkers.
   */
  WalkingIterator(
      Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers)
      throws javax.xml.transform.TransformerException {
    super(compiler, opPos, analysis, shouldLoadWalkers);

    int firstStepPos = OpMap.getFirstChildPos(opPos);

    if (shouldLoadWalkers) {
      m_firstWalker = WalkerFactory.loadWalkers(this, compiler, firstStepPos, 0);
      m_lastUsedWalker = m_firstWalker;
    }
  }

  /**
   * Create a WalkingIterator object.
   *
   * @param nscontext The namespace context for this iterator, should be OK if null.
   */
  public WalkingIterator(PrefixResolver nscontext) {

    super(nscontext);
  }


  /**
   * Get the analysis bits for this walker, as defined in the WalkerFactory.
   *
   * @return One of WalkerFactory#BIT_DESCENDANT, etc.
   */
  public int getAnalysisBits() {
    int bits = 0;
    if (null != m_firstWalker) {
      AxesWalker walker = m_firstWalker;

      while (null != walker) {
        int bit = walker.getAnalysisBits();
        bits |= bit;
        walker = walker.getNextWalker();
      }
    }
    return bits;
  }

  /**
   * Get a cloned WalkingIterator that holds the same
   * position as this iterator.
   *
   * @return A clone of this iterator that holds the same node position.
   */
  public Object clone() throws CloneNotSupportedException {

    WalkingIterator clone = (WalkingIterator) super.clone();

    //    clone.m_varStackPos = this.m_varStackPos;
    //    clone.m_varStackContext = this.m_varStackContext;
    if (null != m_firstWalker) {
      clone.m_firstWalker = m_firstWalker.cloneDeep(clone, null);
    }

    return clone;
  }

  /**
   * Reset the iterator.
   */
  public void reset() {

    super.reset();

    if (null != m_firstWalker) {
      m_lastUsedWalker = m_firstWalker;

      m_firstWalker.setRoot(m_context);
    }

  }

  /**
   * Initialize the context values for this expression
   * after it is cloned.
   *
   * @param context The XPath runtime context for this transformation.
   */
  public void setRoot(int context, Object environment) {

    super.setRoot(context, environment);

    if (null != m_firstWalker) {
      m_firstWalker.setRoot(context);
      m_lastUsedWalker = m_firstWalker;
    }
  }

  /**
   * Returns the next node in the set and advances the position of the
   * iterator in the set. After a NodeIterator is created, the first call
   * to nextNode() returns the first node in the set.
   *
   * @return The next <code>Node</code> in the set being iterated over, or <code>null</code> if
   * there are no more members in that set.
   */
  public int nextNode() {
    if (m_foundLast) {
      return DTM.NULL;
    }

    // If the variable stack position is not -1, we'll have to
    // set our position in the variable stack, so our variable access
    // will be correct.  Iterators that are at the top level of the
    // expression need to reset the variable stack, while iterators
    // in predicates do not need to, and should not, since their execution
    // may be much later than top-level iterators.
    // m_varStackPos is set in setRoot, which is called
    // from the execute method.
    if (-1 == m_stackFrame) {
      return returnNextNode(m_firstWalker.nextNode());
    } else {
      VariableStack vars = m_execContext.getVarStack();

      // These three statements need to be combined into one operation.
      int savedStart = vars.getStackFrame();

      vars.setStackFrame(m_stackFrame);

      int n = returnNextNode(m_firstWalker.nextNode());

      // These two statements need to be combined into one operation.
      vars.setStackFrame(savedStart);

      return n;
    }
  }


  /**
   * Get the head of the walker list.
   *
   * @return The head of the walker list, or null if this iterator does not implement walkers.
   * @xsl.usage advanced
   */
  public final AxesWalker getFirstWalker() {
    return m_firstWalker;
  }

  /**
   * Set the head of the walker list.
   *
   * @param walker Should be a valid AxesWalker.
   * @xsl.usage advanced
   */
  public final void setFirstWalker(AxesWalker walker) {
    m_firstWalker = walker;
  }


  /**
   * Set the last used walker.
   *
   * @param walker The last used walker, or null.
   * @xsl.usage advanced
   */
  public final void setLastUsedWalker(AxesWalker walker) {
    m_lastUsedWalker = walker;
  }

  /**
   * Get the last used walker.
   *
   * @return The last used walker, or null.
   * @xsl.usage advanced
   */
  public final AxesWalker getLastUsedWalker() {
    return m_lastUsedWalker;
  }

  /**
   * Detaches the iterator from the set which it iterated over, releasing
   * any computational resources and placing the iterator in the INVALID
   * state. After<code>detach</code> has been invoked, calls to
   * <code>nextNode</code> or<code>previousNode</code> will raise the
   * exception INVALID_STATE_ERR.
   */
  public void detach() {
    if (m_allowDetach) {
      AxesWalker walker = m_firstWalker;
      while (null != walker) {
        walker.detach();
        walker = walker.getNextWalker();
      }

      m_lastUsedWalker = null;

      // Always call the superclass detach last!
      super.detach();
    }
  }

  /**
   * This function is used to fixup variables from QNames to stack frame
   * indexes at stylesheet build time.
   *
   * @param vars List of QNames that correspond to variables.  This list should be searched
   * backwards for the first qualified name that corresponds to the variable reference qname.  The
   * position of the QName in the vector from the start of the vector will be its position in the
   * stack frame (but variables above the globalsTop value will need to be offset to the current
   * stack frame).
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize) {
    m_predicateIndex = -1;

    AxesWalker walker = m_firstWalker;

    while (null != walker) {
      walker.fixupVariables(vars, globalsSize);
      walker = walker.getNextWalker();
    }
  }

  /**
   * @see com.sun.org.apache.xpath.internal.XPathVisitable#callVisitors(ExpressionOwner,
   * XPathVisitor)
   */
  public void callVisitors(ExpressionOwner owner, XPathVisitor visitor) {
    if (visitor.visitLocationPath(owner, this)) {
      if (null != m_firstWalker) {
        m_firstWalker.callVisitors(this, visitor);
      }
    }
  }


  /**
   * The last used step walker in the walker list.
   *
   * @serial
   */
  protected AxesWalker m_lastUsedWalker;

  /**
   * The head of the step walker list.
   *
   * @serial
   */
  protected AxesWalker m_firstWalker;

  /**
   * @see ExpressionOwner#getExpression()
   */
  public Expression getExpression() {
    return m_firstWalker;
  }

  /**
   * @see ExpressionOwner#setExpression(Expression)
   */
  public void setExpression(Expression exp) {
    exp.exprSetParent(this);
    m_firstWalker = (AxesWalker) exp;
  }

  /**
   * @see Expression#deepEquals(Expression)
   */
  public boolean deepEquals(Expression expr) {
    if (!super.deepEquals(expr)) {
      return false;
    }

    AxesWalker walker1 = m_firstWalker;
    AxesWalker walker2 = ((WalkingIterator) expr).m_firstWalker;
    while ((null != walker1) && (null != walker2)) {
      if (!walker1.deepEquals(walker2)) {
        return false;
      }
      walker1 = walker1.getNextWalker();
      walker2 = walker2.getNextWalker();
    }

    if ((null != walker1) || (null != walker2)) {
      return false;
    }

    return true;
  }

}
